1. Technical Field
The present invention relates to manufacturing a pattern of a light guide panel of a surface light source device used in a liquid crystal display device, a lighting signboard, a cellular phone, a telephone, a Personal Digital Assistant (PDA), a keyboard, an electronic calculator, etc. More particularly, the present invention relates to an apparatus for forming a pattern using a laser, for controlling a luminance characteristic of a light guide panel resulting from an output characteristic of a laser beam, by differentially controlling lengths of light guide patterns and forming the light guide patterns in a plurality of light guide panels.
2. Description of the Related Art
Commonly, a light guide panel, which is a plate for providing a path for uniformly scattering and diffusing light scanned from a light source, is being applied to a light receiving flat display device such as a liquid crystal display device, or a surface light source device used in a lighting signboard, etc.
FIG. 1 is a cross section schematically illustrating a conventional surface light source device.
Referring to FIG. 1, the conventional surface light source device 10 includes a light guide panel 11, a reflective sheet 12 installed below the light guide panel 11, a light source 13 installed at one side of the light guide panel 11, and a cover member 14 covering the light source 13. As the light source 13, a cold cathode fluorescent lamp, a Light Emitting Diode (LED), etc. can be used. In the light guide panel 11, a plurality of light guide patterns 15 are formed by using a bead-shaped Oxide Titanium (TiO2) and ink including glass, acryl, etc. to scatter and diffuse light incident on one surface of a transparent acrylic resin. In the surface light source device 10, light irradiated from the light source 13 is incident on the light guide panel 11, and the incident light is guided through the light guide panel 11 as indicated by arrows. After that, the guided light is reflected at relatively uniform illumination in each part by the reflective sheet 12 and the light guide patterns 15. After that, the reflected light passes through a diffuse sheet 16 and again passes through a prism sheet 17 to direct toward the front.
On the other hand, as a method for forming the light guide patterns 15 of the light guide panel 11, there is a method using a Carbon Dioxide (CO2) laser. However, in the Carbon Dioxide (CO2) laser, output characteristic is lowered according to distance. Thus, in case that a plurality of light guide panels 11 are simultaneously manufactured on the basis of the same length information of light guide patterns 15, there is a problem of making a luminance characteristic of each of the light guide panels 11 non-uniform.
Also, position and length information on each light guide pattern 15 to be formed in the light guide panel 11 are generally previously stored in a pattern storing module (not shown), and this information is read out from the pattern storing module (not shown) to form the light guide patterns 15. In this case, there is a problem of the occurrence of an exterior warp phenomenon in which it is seen that the light guide patterns 15 formed in the light guide panel 11 are seemingly curved or warped along their edges due to several main causes.